EDIT: that site doesn't allow Firefox to view it full sized in a separate window for some reason
It's either photoshop or scarring from a recurring polynoidal cycst. Its a common medical condition that usually affects men but women get it as well. The area where your ass cheeks meet your lower back are riddled with sub-cutaneous folded skin which contains little spaces. these spaces can get infected in a lot of ways. Once infected a cyst/boil forms, busts open and drains. Afterwards the cyst will reform again and again going through a cycle and like people with acne scars, it turns the tissue into a disgusting area of holes if its not treated after the first several appear. The treatement is to slice it open and scrape the entire area out to the tail bone. It's not unheard of to see something like this otherwise hot chick has.
*terminating disgusting story of the day mode* :yuck2: